Base station apparatus, communication terminal apparatus, and communication method

ABSTRACT

An assignment section  101  determines communication resource assignment to communication terminals based on a transmission rate at which communication is possible for each subcarrier of each communication terminal, and instructs a buffer section  102  to output forward transmission data. In addition, the assignment section  101  instructs a frame creation section  103  to perform forward transmission data symbolization, and also outputs a signal indicating communication resource assignment to each communication terminal. The buffer section  102  holds forward transmission data, and outputs forward transmission data to the frame creation section  103  in accordance with instructions from the assignment section  101.  The frame creation section  103  symbolizes a resource assignment signal and transmission data to create a frame, which it outputs to a spreading section  104.

This is a broadening continuation reissue application (as opposed to acontinuation of a reissue application). The parent reissue isapplication Ser. No. 12/613,256 filed Nov. 5, 2009 (now U.S. Pat. No.Re. 43,614), which is a reissue application of U.S. Pat. No. 7,292,862(application Ser. No. 09/958,956) which has a 371 date of Dec. 31, 2001,and which issued on Nov. 6, 2007 and which is a national stage ofPCT/JP2001/01056 filed Feb. 15, 2001, which is based on JapaneseApplication No. 2000-038877 filed Feb. 16, 2000, the entire contents ofeach of which are incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a base station apparatus, communicationterminal apparatus, and communication method.

BACKGROUND ART

In a cellular communication system, one base station performs radiocommunication with a plurality of communication terminalssimultaneously, and therefore, as demand has increased in recent years,so has the need for higher transmission efficiency.

One technology for increasing the transmission efficiency of a downlinkfrom a base station to a communication terminal is HDR (High Data Rate).HDR is a method whereby scheduling for assigning communication resourcesto communication terminals is performed by time division, and datatransmission efficiency is further improved by setting the transmissionrate for each communication terminal according to the communicationquality. This method is suitable for connection via the Internet and thelike.

The operations performed by a base station and communication terminalsin order to set the transmission rate in HDR will be described belowusing FIG. 1. In FIG. 1, a base station 11 is currently performingcommunication with communication terminals 12 to 14.

First, the base station 11 transmits a pilot signal to each ofcommunication terminals 12 to 14. Each of communication terminals 12 to14 estimates the communication quality according to the SIR (Signal toInterference Ratio) of the received pilot signal, etc., and finds atransmission rate at which communication with the base station ispossible. Then, based on the transmission rate at which communication ispossible, each of communication terminals 12 to 14 selects acommunication mode, which is a combination of packet length, errorcorrection, and modulation method, and transmits a signal indicating thecommunication mode to the base station 11.

Based on the communication mode selected by each of communicationterminals 12 to 14, the base station 11 performs scheduling, sets atransmission rate for each communication terminal, and sends a signal toeach of communication terminals 12 to 14 via a control channelindicating communication resource assignment to each communicationterminal.

The base station 11 then transmits only data for the relevantcommunication terminal in its assigned time. For example, if time t1 hasbeen assigned to communication terminal 12, the base station 11transmits data for communication terminal 12 in time t1, and does nottransmit to communication terminals 13 and 14.

In this way, data transmission efficiency has conventionally beenincreased for the overall system by setting a transmission rate for eachcommunication terminal according to the communication quality by meansof HDR.

Here, the communication quality of some bands may degrade due tofrequency selective fading. Also, the band portion for whichcommunication quality degrades differs for each communication terminal.

In FIG. 2, for example, communication terminal 12 has good communicationquality on the high-frequency side but poor communication quality on thelow-frequency side, while communication terminal 13 has goodcommunication quality on the low-frequency side but poor communicationquality on the high-frequency side, and communication terminal 14 alsohas good communication quality on the low-frequency side but poorcommunication quality on the high-frequency side.

However, as the above-described conventional base station andcommunication terminals perform communication using the entire band, aproblem is that communication quality degrades and transmissionefficiency falls in a band affected by frequency selective fading.

DISCLOSURE OF THE INVENTION

It is an objective of the present invention to provide a base stationapparatus, communication terminal apparatus, and communication methodthat enable high transmission efficiency to be maintained even in anenvironment affected by frequency selective fading.

This objective is achieved by estimating the communication quality foreach subcarrier in each communication terminal, and transmitting datafrom the base station to each communication terminal using a subcarrierfor which the communication quality is good.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is drawing showing a communication mode using the conventionalHDR method;

FIG. 2 is a drawing showing the effects of frequency selective fading ina communication band;

FIG. 3 is a block diagram showing the configuration of a base stationaccording to Embodiment 1 of the present invention;

FIG. 4 is a block diagram showing the configuration of a communicationterminal according to the above-mentioned embodiment;

FIG. 5 is a drawing showing the effects of frequency selective fadingand band assignment in communication between a base station andcommunication terminals according to the above-mentioned embodiment:

FIG. 6 is a drawing showing an example of resource assignment in slotsfor transmission from a base station to communication terminalsaccording to the above-mentioned embodiment;

FIG. 7 is a block diagram showing the configuration of a base stationaccording to Embodiment 2 of the present invention;

FIG. 8 is a drawing showing communication resource assignment accordingto the above-mentioned embodiment; and

FIG. 9 is a block diagram showing the configuration of a communicationterminal according to Embodiment 3 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference now to the attached drawings, embodiments of the presentinvention will be explained in detail below.

(Embodiment 1)

FIG. 3 is a block diagram showing the configuration of a base stationaccording to Embodiment 1 of the present invention.

In FIG. 3, an assignment section 101 determines communication resourceassignment to each communication terminal based on a transmission rateat which communication is possible for each subcarrier of eachcommunication terminal estimated by a channel estimation section 114 tobe described below, and gives instructions to a buffer section 102 forforward transmission data output. The assignment section 101 alsoinstructs a frame creation section 103 to perform forward transmissiondata symbolization, and outputs a signal indicating communicationresource assignment to each communication terminal (hereinafter referredto as “resource assignment signal”). In addition, the assignment section101 indicates to a spreading section 104 a spreading code to bemultiplied by the forward transmission data.

The buffer section 102 holds forward transmission data, and outputsforward transmission data to the frame creation section 103 inaccordance with instructions from the assignment section 101.

The frame creation section 103 generates a pilot signal, symbolizesforward transmission data output from the buffer section 102 inaccordance with instructions from the assignment section 101, andinserts a pilot signal at predetermined intervals to create a frame,which it outputs to the spreading section 104. The frame creationsection 103 also symbolizes the resource assignment signal andtransmission data to create a frame, which it outputs to the spreadingsection 104.

At the start of communication, the frame creation section 103 outputsonly a pilot signal to the spreading section 104.

The spreading section 104 spreads frame creation section 103 outputsignals in accordance with instructions of the assignment section 101,and outputs them to an IFFT section 105.

The IFFT section 105 performs an inverse fast Fourier transform of thespreading section 104 output signals, and outputs the resulting signalto a D/A converter 106. The D/A converter 106 performs digital-to-analogconversion of the IFFT section 105 output signal, and outputs theresulting signal to a transmit RF section 107. The transmit RF section107 converts the frequency of the D/A converter 106 output signal to aradio frequency, and outputs this signal to an antenna 108. The antenna108 transmits the transmit RF section 107 output signal to acommunication terminal.

Antenna 111 receives a signal transmitted by radio from a communicationterminal and outputs it to a receive RF section 112. The receive RFsection 112 converts the received signal frequency to baseband andoutputs it to a demodulation section 113.

The demodulation section 113 demodulates the baseband signal and outputsreceived data. In addition, the demodulation section 113 outputs a datarate request (hereinafter referred to as “DRR”) signal included in thebaseband signal to the channel estimation section 114. The DRR signalwill be explained later together with a description of the communicationterminal configuration.

Based on the DRR signal, the channel estimation section 114 estimates atransmission rate at which communication with each communicationterminal is possible for each subcarrier, and outputs the estimationresults to the assignment section 101.

A receive RF section 112, demodulation section 113, and channelestimation section 114 are provided for each user.

FIG. 4 is a block diagram showing the configuration of a communicationterminal according to this embodiment.

In FIG. 4, an antenna 201 receives a radio signal transmitted from thebase station shown in FIG. 3, and outputs it to a receive RF section202. In addition, the antenna 201 transmits a transmit signal outputfrom a transmit RF section 210 to the base station shown in FIG. 3 as aradio signal.

The receive RF section 202 converts the frequency of a radio frequencysignal received by the antenna 201 to baseband, and outputs it to an A/Dconverter 203. The A/D converter 203 performs analog-to-digitalconversion of the baseband signal and outputs it to an FFT section 204.The FFT section 204 performs a fast Fourier transform of the A/Dconverter 203 output signal and outputs the results to a despreadingsection 205. The despreading section 205 despreads the FFT section 204output signals and outputs the resulting signals to an SIR determinationsection 206.

The SIR determination section 206 extracts a pilot signal from thedespreading section 205 output signals, and outputs components otherthan the pilot signal to a subcarrier selection section 211. Inaddition, the SIR determination section 206 finds the SIR for eachsubcarrier based on the extracted pilot signal, and outputs it to atransmission rate calculation section 207.

The transmission rate calculation section 207 calculates a possibletransmission rate with respect to the base station for each subcarrierbased on the SIR, and outputs the calculation results to a requestsignal creation section 208.

Based on the calculation results of the transmission rate calculationsection 207, the request signal creation section 208 creates a DRRsignal for requesting the subcarrier transmission rate of eachsubcarrier from the base station, which it outputs to a modulationsection 209. The modulation section 209 modulates the DRR signal andinbound transmission data, and outputs the result to the transmit RFsection 210.

The transmit RF section 210 performs frequency conversion of themodulation section 209 output signal to radio frequency, and outputsthis signal to the antenna 201.

In accordance with notification from a reception control section 214,the subcarrier selection section 211 selects components other than thepilot signal output from the SIR determination section 206 in eachsubcarrier, and outputs these to a P/S conversion section 212.

The P/S conversion section 212 performs parallel-to-serial conversion ofthe output signals from the subcarrier selection section 211 and outputsthe resulting signal to a demodulation section 213.

The demodulation section 213 demodulates the output signal from the P/Sconversion section 212 to extract received data, and also outputs acontrol signal to the reception control section 214.

Based on the control signal, the reception control section 214 reportsthe subcarrier by which a signal addressed to this station is carried tothe subcarrier selection section 211.

Next, the signal flow until determination of the downlink transmissionrate between the base station shown in FIG. 3 and the communicationterminal shown in FIG. 4 will be described.

First, a pilot signal is created in the frame creation section 103 ofthe base station. The pilot signal is spread by the spreading section104 together with forward transmission data, undergoes an inverse fastFourier transform by the IFFT section 105, digital-to-analog conversionby the D/A converter 106, and frequency conversion to a radio frequencyby the transmit RF section 107, and is transmitted to the communicationterminal from the antenna 108.

In the communication terminal, a signal received by the antenna 201undergoes frequency conversion to baseband by the receive RF section202, analog-to-digital conversion by the A/D converter 203, and a fastFourier transform by the FFT section 204, and is despread by thedespreading section 205. The pilot signal is then extracted from thedespreading section 205 by the SIR determination section 206, and theSIR is found based on the pilot signal.

Then the transmission rate calculation section 207 calculates atransmission rate at which communication is possible for each subcarrierbased on the SIR, and the request signal creation section 208 creates aDRR signal for requesting the transmission rate of each subcarrier.

The DRR signal is modulated by the modulation section 209 together withinbound transmission data, undergoes frequency conversion to a radiofrequency by the transmit RF section 210, and is transmitted to the basestation from the antenna 201.

In the base station, a signal received by the antenna 111 undergoesfrequency conversion to baseband by the receive RF section 112 and isdemodulated by the demodulation section 113, and the DRR signal includedin the demodulated baseband signal is output to the channel estimationsection 114. Based on the DRR signal, the channel estimation section 114estimates for each subcarrier a transmission rate at which communicationwith each terminal is possible.

Based on the transmission rate at which communication is possible foreach subcarrier of each communication terminal, the assignment section101 determines communication resource assignment to each communicationterminal, and outputs a resource assignment signal to the frame creationsection 103.

The resource assignment signal is despread by the spreading section 104together with forward transmission data, undergoes an inverse fastFourier transform by the IFFT section 105, digital-to-analog conversionby the D/A converter 106, and frequency conversion to a radio frequencyby the transmit RF section 107, and is sent to each communicationterminal from the antenna 108 via a control channel.

Based on the resource assignment signal, each communication terminalreceives data in the reception time and on the subcarrier assigned toit.

Outbound transmission data to be sent to communication terminals fromthe base station is stored in the buffer section 102 until communicationresource assignment has been decided. After a resource assignment signalhas been transmitted, forward transmission data is output from thebuffer section 102 to the frame creation section 103 in accordance withthe resource assignment signal, and symbolized.

When forward transmission data is symbolized, the subcarrier andcommunication rate are set based on the resource assignment signal.

Symbolized forward transmission data undergoes an inverse fast Fouriertransform by the IFFT section 105, digital-to-analog conversion by theD/A converter 106, and frequency conversion to a radio frequency by thetransmit RF section 107, and is transmitted from the antenna 108.

Next, an actual example of communication resource assignment will bedescribed.

FIG. 5 is a drawing showing the effects of frequency selective fadingand band assignment in communication between a base station andcommunication terminals.

The bold lines in FIG. 5 show the effect of fading on band communicationquality.

The user 1 communication terminal has good communication quality inbands f4 and f5 but poor communication quality in bands f1, f2, and f3.The user 2 communication terminal has good communication quality inbands f2 and f3 but poor communication quality in bands f1, f4, and f5.And the user 3 communication terminal has good communication quality inband f1 but poor communication quality in bands f2, f3, f4, and f5.

Thus, in communication with the respective communication terminals,bands with good communication quality are assigned.

FIG. 6 is a drawing showing an example of resource assignment in slotsfor transmission from a base station to communication terminals. Thehorizontal axis shows times at which slot transmission is performed.

In data transmission from the base station, control signals and data areincluded in a slot of a predetermined length. The control signalsinclude signals that indicate the data transmission timing andtransmission rate to each user communication terminal, and data isarranged according to the control signal information.

In FIG. 6, subcarrier 1 uses band f1, subcarrier 2 uses band f2,subcarrier 3 uses band f3, subcarrier 4 uses band f4, and subcarrier 5uses band f5.

The base station assigns band f1 to communication with the user 3communication terminal, assigns bands f2 and f3 to communication withthe user 2 communication terminal, and assigns bands f4 and f5 tocommunication with the user 3 communication terminal.

User 3 data is assigned to the subcarrier 1 time slot, user 2 data isassigned to the subcarrier 2 time slot, user 2 data is assigned to thesubcarrier 3 time slot, user 1 data is assigned to the subcarrier 4 timeslot, and user 1 data is assigned to the subcarrier 5 time slot.

Thereafter, bands with good communication quality are also assigned tousers 4, 5, and 6.

By estimating the communication quality for each subcarrier in eachcommunication terminal and transmitting data from the base station toeach communication terminal using a subcarrier with good communicationquality in this way, it is possible to maintain high transmissionefficiency even in an environment subject to frequency selective fading.Also, by receiving data on each subcarrier, it is possible to maintainhigh transmission efficiency even in an environment subject to frequencyselective fading.

A resource assignment signal can be transmitted using a differentfrequency or different modulation method from a data signal.

Also, a resource assignment signal can be transmitted for eachsubcarrier, as subcarrier-unit resource assignment information. In thiscase, resource assignment signals can be simplified by having the basestation create resource assignment signals in each subcarrier andtransmit them using the same subcarrier as the data, and havingcommunication terminals received data in each subcarrier based on areceived communication resource assignment signal.

In this embodiment, a station's own address symbol is extracted frompost-despreading symbols output from the SIR determination section 206,but with the present invention, a station's own address symbol can beextracted as long as it is a symbol after a fast Fourier transform andbefore demodulation.

In this case, in FIG. 3, a symbol is output from the FFT section 204,despreading section 205, or P/S conversion section 212 to the subcarrierselection section 211.

(Embodiment 2)

FIG. 7 is a block diagram showing the configuration of a base stationaccording to Embodiment 2 of the present invention.

Parts identical to those in FIG. 3 are assigned the same referencenumerals as in FIG. 3 and their detailed explanations are omitted.

The base station apparatus in FIG. 7 comprises a plurality of spreadingsections 502, 512, 522, and a plurality of frame creation sections 501,511, 521, and differs from the base station in FIG. 3 in that a signalwith a low spreading ratio is transmitted in a band with goodcommunication quality, and a signal with a high spreading ratio istransmitted in a band with poor communication quality due to the effectsof frequency selective fading, etc.

In FIG. 7, an assignment section 101 determines communication resourceassignment to each communication terminal based on a transmission rateat which communication is possible for each subcarrier of eachcommunication terminal estimated by a channel estimation section 114,and gives instructions to a buffer section 102 for forward transmissiondata output. The assignment section 101 also instructs frame creationsections 501, 511, 521 to perform forward transmission datasymbolization, and outputs a resource assignment signal. In addition,the assignment section 101 indicates to spreading sections 502, 512, 522respectively a spreading code to be multiplied by the forwardtransmission data.

Frame creation sections 501, 511, 521 generate a pilot signal, symbolizeforward transmission data output from the buffer section 102 inaccordance with instructions from the assignment section 101, and inserta pilot signal at predetermined intervals to create a frame, which theyoutput to spreading sections 502, 512, 522. At the start ofcommunication, frame creation sections 501, 511, 521 output only a pilotsignal to spreading sections 502, 512, 522.

Spreading sections 502, 512, 522 spread the frame creation section 501,511, 521 output signals using the respective spreading codes indicatedby the assignment section 101, and output them to an IFFT section 105.

By having spreading sections 502, 512, 522 perform spreadingindividually using spreading codes indicated by the assignment section101 in this way, it is possible to transmit symbols with a spreadingratio set for individual communication terminals for the respectivesubcarriers.

Next, communication resource assignment will be described. FIG. 8 is adrawing showing communication resource assignment according toEmbodiment 2.

In FIG. 8, the horizontal axis shows frequencies and the vertical axisshows communication quality. The bold lines show variations incommunication quality due to frequency selective fading in communicationwith each communication terminal.

The user 1 communication terminal has good communication quality inbands f4 and f5, rather poor communication quality in bands f2 and f3,and poor communication quality in band f1. The user 2 communicationterminal has good communication quality in bands f2 and f3, rather poorcommunication quality in bands f1 and f4, and poor communication qualityin band f5.

Thus, the base station transmits signals with a low spreading ratio tothe user 1 communication terminal in bands f4 and f5, and transmitssignals with a high spreading ratio in lower-frequency bands f2 and f3.

Also, the base station transmits signals with a low spreading ratio tothe user 1 communication terminal in bands f2 and f3, and transmitssignals with a high spreading ratio in lower-frequency bands f1 and f4.

In this way, a communication apparatus of the present invention, bytransmitting signals with a low spreading ratio in bands with goodcommunication quality, and transmitting signals with a high spreadingratio in bands with poor communication quality due to the effects offrequency selective fading, etc., can transmission data at a hightransmission rate by transmitting signals with a low spreading ratio inbands with good communication quality.

Also, by transmitting a signal with a high spreading ratio in a bandwith poor communication quality, it is possible to reduce the influenceon other signals spread on the same subcarrier.

(Embodiment 3)

FIG. 9 is a block diagram showing the configuration of a communicationterminal according to Embodiment 3 of the present invention. Partsidentical to those in FIG. 4 are assigned the same reference numerals asin FIG. 4 and their detailed explanations are omitted.

In FIG. 9, an SIR determination section 701 finds the ratio of theinterference component to a signal in another band based on a receivedpilot signal, and outputs the result to a transmission rate calculationsection 207 as an SIR.

In addition, the SIR determination section 701 determines a signal thatmeets a predetermined threshold value from among received signals to bea signal for communication with that station and outputs it to a P/Sconversion section 212, and discards signals that do not meet thepredetermined threshold value as interference signals.

By estimating communication quality for each subcarrier in eachcommunication terminal and transmitting data from the base station toeach communication terminal using a subcarrier with good communicationquality in this way, it is possible to maintain high transmissionefficiency even in an environment subject to frequency selective fading.Also, by receiving data on each subcarrier, it is possible to maintainhigh transmission efficiency even in an environment subject to frequencyselective fading.

In the embodiments of the present invention, a transmission rate atwhich communication with the base station is possible is calculatedbased on an SIR, but this is not a limitation, and a value thatindicates the quality of a communication line, such as signal-to-noiseratio, may also be used as a basis for calculating a transmission rate.

Also, in the embodiments of the present invention, despreadingprocessing is carried out on symbols after a fast Fourier transform, butthis is not a limitation, and it is also possible for a fast Fouriertransform to be carried out on symbols after subcarrier selection orafter parallel-to-serial conversion.

Moreover, the present invention can be applied to any communicationmethod as long as it uses frequency division.

As can be seen from the above descriptions, it is possible to estimatethe communication quality for each subcarrier in each communicationterminal, and to transmission data from a base station to eachcommunication terminal using a subcarrier for which the communicationquality is good.

This application is based on the Japanese Patent Application No.2000-038877 filed on Feb. 16, 2000, entire content of which is expresslyincorporated by reference herein.

The invention claimed is:
 1. A base station apparatus comprising: a receiver that receives a signal representing communication quality estimated per subcarrier in a communication terminal apparatus of a communicating party; an assigner that assigns subcarriers for use in communication with the communication terminal apparatus in accordance with the signal representing communication quality; and a transmitter that transmits data to the communication terminal apparatus using the subcarriers assigned by the assigner.
 2. The base station apparatus of claim 1 wherein the transmitter transmits subcarrier assignment information per subcarrier.
 3. The base station apparatus of claim 1, wherein the assigner assigns the subcarriers, for use in communication with the communication terminal apparatus, per time slot.
 4. The base station apparatus of claim 1, wherein the assigner determines a spreading factor, of the data transmitted from the transmitter, in accordance with the signal representing communication quality.
 5. A communication terminal apparatus comprising a demodulator that demodulates a signal, addressed to said communication terminal apparatus and carried by subcarriers, in accordance with the subcarrier assignment information transmitted from the base station apparatus of claim
 2. 6. The communication terminal apparatus of claim 5, wherein the demodulator performs threshold determination of quality of the signal addressed to said communication terminal apparatus and demodulates said signal when the quality is above a predetermined threshold.
 7. A communication method comprising: receiving a signal at a base station apparatus, said signal representing communication quality estimated per subcarrier in a communication terminal apparatus of a communicating party; assigning subcarriers for use in communication with the communication terminal apparatus in accordance with the signal representing communication quality; transmitting subcarrier assignment information and data to the communication terminal apparatus using the assigned subcarriers; and demodulating a signal addressed to the communication terminal apparatus and carried by the subcarriers, in accordance with the subcarrier assignment information transmitted from the base station apparatus.
 8. A communication method comprising: receiving a signal at a base station apparatus, said signal representing communication quality estimated per subcarrier in a communication terminal apparatus of a communicating party; assigning subcarriers for use in communication with the communication terminal apparatus in accordance with the signal representing communication quality; transmitting data to the communication terminal apparatus using the assigned subcarriers; and performing threshold determination of quality of a signal addressed to the communication terminal apparatus and demodulating said signal when the quality is above a predetermined threshold.
 9. A communication method comprising: receiving, at a base station apparatus, a signal transmitted from a terminal apparatus, the signal indicating communication quality calculated in said terminal apparatus for each of bands, into which a frequency domain comprised of subcarriers is divided, and each of the bands comprising a subcarrier; assigning, to said terminal apparatus, a resource comprised of consecutive subcarriers in a part of the bands; transmitting, from said base station apparatus to said terminal apparatus, assignment information indicating the resource assigned to said terminal apparatus; and transmitting, from said base station apparatus to said terminal apparatus, data using the resource, wherein the assignment information is transmitted using another resource which is different from the resource assigned to said terminal apparatus.
 10. A communication method comprising: receiving, at a base station apparatus, a signal transmitted from a terminal apparatus, the signal indicating communication quality calculated in said terminal apparatus for each of bands, into which a frequency domain comprised of subcarriers is divided, and each of the bands comprising a subcarrier; assigning, to said terminal apparatus, a resource comprised of consecutive subcarriers in a part of the bands; transmitting, from said base station apparatus to said terminal apparatus, assignment information indicating the resource assigned to said terminal apparatus; and transmitting, from said base station apparatus to said terminal apparatus, data using the resource, wherein the assignment information is transmitted with a modulation scheme which is different from that for the data.
 11. A communication method comprising: transmitting, from a terminal apparatus to a base station apparatus, a signal indicating communication quality calculated for each of bands, into which a frequency domain comprised of subcarriers is divided, and each of the bands comprising a subcarrier; receiving, at said terminal apparatus, assignment information, which indicates a resource assigned to said terminal apparatus and which is transmitted from said base station apparatus to said terminal apparatus, the resource being comprised of consecutive subcarriers in a part of the bands; and receiving, at said terminal apparatus, data transmitted from said base station apparatus using the resource, which said base station apparatus assigns to said terminal apparatus, in accordance with the assignment information, wherein the assignment information is transmitted using another resource which is different from the resource assigned to said terminal apparatus.
 12. A communication method comprising: transmitting, from a terminal apparatus to a base station apparatus, a signal indicating communication quality calculated for each of bands, into which a frequency domain comprised of subcarriers is divided, and each of the bands comprising a subcarrier; receiving, at said terminal apparatus, assignment information, which indicates a resource assigned to said terminal apparatus and which is transmitted from said base station apparatus to said terminal apparatus, the resource being comprised of consecutive subcarriers in a part of the bands; and receiving, at said terminal apparatus, data transmitted from said base station apparatus using the resource, which said base station apparatus assigns to said terminal apparatus, in accordance with the assignment information, wherein the assignment information is transmitted with a modulation scheme which is different from that for the data.
 13. A base station apparatus comprising: a receiver configured to receive a signal transmitted from a terminal apparatus, the signal indicating communication quality calculated in said terminal apparatus for each of bands, into which a frequency domain comprised of subcarriers is divided, and each of the bands comprises a subcarrier; an assigner configured to assign, to said terminal apparatus, a resource comprised of consecutive subcarriers in a part of the bands; a transmitter configured to transmit, to said terminal apparatus, assignment information indicating the resource assigned to said terminal apparatus, and configured to transmit, to said terminal apparatus, data using the resource, wherein the assignment information is transmitted using another resource which is different from the resource assigned to said terminal apparatus.
 14. A base station apparatus comprising: a receiver configured to receive a signal transmitted from a terminal apparatus, the signal indicating communication quality calculated in said terminal apparatus for each of bands, into which a frequency domain comprised of subcarriers is divided, and each of the bands comprises a subcarrier; an assigner configured to assign, to said terminal apparatus, a resource comprised of consecutive subcarriers in a part of the bands; a transmitter configured to transmit, to said terminal apparatus, assignment information indicating the resource assigned to said terminal apparatus, and configured to transmit, to said terminal apparatus, data using the resource, wherein the assignment information is transmitted with a modulation scheme which is different from that for the data.
 15. A terminal apparatus comprising: a transmitter configured to transmit, to a base station apparatus, a signal indicating communication quality calculated for each of bands, into which a frequency domain comprised of subcarriers is divided, and each of the bands comprises a subcarrier; and a receiver configured to receive assignment information, which indicates a resource assigned to said terminal apparatus and which is transmitted from said base station apparatus, the resource being comprised of consecutive subcarriers in a part of the bands, and configured to receive data transmitted from said base station apparatus using the resource, which said base station apparatus assigns to said terminal apparatus, in accordance with the assignment information, wherein the assignment information is transmitted using another resource which is different from the resource assigned to said terminal apparatus.
 16. A terminal apparatus comprising: a transmitter configured to transmit, to a base station apparatus, a signal indicating communication quality calculated for each of bands, into which a frequency domain comprised of subcarriers is divided, and each of the bands comprises a subcarrier; and a receiver configured to receive assignment information, which indicates a resource assigned to said terminal apparatus and which is transmitted from said base station apparatus, the resource being comprised of consecutive subcarriers in a part of the bands, and configured to receive data transmitted from said base station apparatus using the resource, which said base station apparatus assigns to said terminal apparatus, in accordance with the assignment information, wherein the assignment information is transmitted with a modulation scheme which is different from that for the data. 